Ram pickup shows one issue that is in fact multiple faults.

This was an unusual case of a vehicle with multiple problems presenting as a single issue. Usually when we do a diagnostic analysis, the root cause of the problem can be traced to a single fault. Because of modern vehicle networking and module interconnectivity the problem may manifest itself over several systems, but the root cause is usually one fault.

No problem initially

We had a 2019 Ram 1500 pickup sent to us from a used car dealer with a battery drain. The dealer had bought the vehicle at an auction, had no history on the vehicle but stated that they thought the problem began after the interior was detailed. We initially inspected the vehicle at the dealership, but the vehicle was not acting up on first inspection. We had the vehicle brought to our location so we could do a more in-depth diagnosis. After observing the vehicle for a couple of days we measured a 4-amp draw using an inductive amp clamp. This was way too much—we like to see modern vehicles under 100 ma.

A code scan was performed next, and we observed multiple “U” codes as well as codes for low system voltage (understandable) and codes for several modules failing to communicate. Also, while we were observing the vehicle after shutting the vehicle off, the cluster kept coming on and off. Modules that turn on and off randomly are usually an indication of internal module failure or the vehicle network not shutting down correctly. We performed a topology scan with the vehicle powered up and with the vehicle powered down.

Figure 1 shows the scan with the vehicle on, and Figure 2 shows the scan with the vehicle off.

EDM issue

There was no doubt that there was a problem with the EDM (External Disc Module) as it showed as being offline all the time. There was also an additional problem in that the vehicle had many modules staying alive after shutting down.

We scoped the CAN BUS next and found that the network was not going to sleep. The normal procedure for this is to check that the gateway is getting the ignition off message, it was and then we started eliminating modules on the BUS. When the Steering Column Control Module was unplugged, the BUS powered down and the vehicle went to sleep. The Instrument cluster stopped turning on and off.

We went back and measured the draw with the network properly shut down. This time we measured 2 amps. This is half the original draw but still too high. This is the unusual part. The vehicle must have another draw.

This time we went to power distribution and using a low amp clamp determined that the draw was coming from the interior fuse box. We then used an Amp Hound tester and probed the fuses in the interior fuse box to determine which fuse was drawing current. It was quickly determined that fuse #43 was the culprit. A wiring diagram was consulted to determine which components were fed off of this fuse and we discovered that the EDM was on the #43 fuse. From our previous topology scan we remembered that the EDM was never online, so we removed some trim panels to access the EDM. The EDM was unplugged, and the vehicle was again checked for a draw. This time we measured 65 ma. This was acceptable.

Two unrelated draws

To sum this up, the vehicle had two unrelated draws. The first was the Steering Column Control Module not allowing the vehicle to power down properly and the EDM with an internal failure that was constantly drawing power.

Because this is unusual in that there were two separate problems, we suspect this occurred when the vehicle was detailed, and that somehow, water got into the two modules. This is speculation on my part but seem logical. Following established diagnostic procedures, we were able to identify the two faults and fix the vehicle.